1. Field of the Invention
The present invention relates generally to metal oxide semiconductor (MOS) operational transconductance amplifier for providing linear amplification of an analog input voltage to produce an amplified analog output current, and more specifically to a MOS operational transconductance amplifier suitable for LSI implementation.
2. Description of the Related Art
An operational transconductance amplifier is described in a paper "Design of Linear CMOS Transconductance Elements", Nedungadi et al, IEEE Transactions on Circuits and Systems, Vol. CAS-31, No. 10, October 1984, pages 891-894. The known transconductance amplifier includes four transistors connected in an unbalanced cross-coupled quad cell configuration for supplying a bias current to a MOS differential pair to which an input voltage is applied. To optimize the bias current for linear operation of the transconductance amplifier, it is necessary to set the width-to-length ratio of the channels of the quad cell transistors at 1:(1+2/.sqroot.3). However, the ratio of this value is impractical for LSI implementation in so far as linear amplification is concerned.